The present invention relates to a backlight illuminator including a plurality of linear light sources arranged in parallel. More particularly, the present invention relates to a backlight illuminator which is used to illuminate, for example, a liquid crystal display device, and an illumination display board from the rear surface or back side.
Applicant has proposed a backlight illuminator in the co-pending Japanese Patent Application No. 2000-113423.
The backlight illuminator proposed in the co-pending application includes a plurality of linear light sources and a series of reflectors. The plural linear light sources are arranged in parallel at predetermined intervals facing an illumination surface of the backlight illuminator. With this arrangement, each linear light source illuminates each of allocated illumination areas, thereby illuminating the entire illumination surface of the backlight illuminator. The reflector is in the shape of symmetrical continuous wave, and disposed behind the linear light sources along the direction of arrangement of the light sources in order to reflect light back to the illumination surface of the backlight illuminator.
The reflector is made of a high reflective thin sheet material. More specifically, the sheet material is shaped, by means of bending or curving or otherwise, to have the reflective surfaces which includes seven or eight reflective surfaces. Each of the reflective surfaces reflects light back to the surface to be illuminated on which the reflected light is partially overlapped so as to achieve illumination which ensures the highest possible uniformity of brightness all over the surface to be illuminated.
This illuminator ensures a high brightness and high uniformity of brightness for the surface to be illuminated. However, the reflector used in the illuminator is liable to break during the bending or curving process of the reflector, if the reflector is fabricated by using a white foamed resin, such as, for example, a polyester foamed sheet having a foamed surface on its surface, as a reflective material, because of low impact resistance of the foamed resin although the resin is generally elastic. Further, it is difficult to fabricate the reflector to have the reflective surfaces at a required angle. In this type of illuminator, a thin cold cathode fluorescent tube having a tube diameter of approximately 3 mm to 4 mm is used as a linear light source so that the overall illuminator may be thin. In addition, the fluorescent tubes are arranged with a lamp pitch of approximately 24 mm to 30 mm, and the small diameter of the cold cathode fluorescent tube is used. In consequence, the width of the corresponding reflective surfaces of the reflector must be reduced. As a result, it is required to fabricate the reflective surfaces in a high precision which makes it difficult to manufacture the reflector.
The present invention has been made to solve the above-mentioned problems.
Accordingly, it is an object of the present invention to provide a backlight illuminator having a reflector above which a plurality of parallel light sources are arranged. According to the present invention, it is possible to facilitate manufacturing the reflector by reducing the number of reflective surfaces to be formed on the reflector and also by simplifying the shape of the reflector, and also to realize illumination with a high brightness and high uniformity by effectively eliminating deterioration in brightness and uniformity on the surface to be illuminated due to the simplification of the shape of the reflector.
After extensive research and experimentation to overcome the foregoing problems, the applicant have completed the present invention based on findings as to the reflector on which a plurality of parallel linear light sources are arranged, and the shape of the reflective surfaces of the reflector.
Firstly, the description is given with regard to a reflective region having reflective surfaces formed for each light source. More specifically, the reflective region is formed in symmetry about each light source. The reflective region comprises three reflective surfaces including a reflective surface close to the light source, an intermediate reflective surface, and a reflective surface distant from the light source. The reflective surface close to the light source is formed into a flat horizontal reflective surface. The intermediate reflective surface is formed into either an angled reflective surface slanted with respect to the horizontal reflective surface or a curved reflective surface concavely curved with respect the horizontal reflective surface. The reflective surface distant from the light source is formed into an angled reflective surface slanted with respect to the horizontal reflective surface. Thus, the number of reflective surfaces for each light source can be minimized, which makes it possible to precisely form the shape of each reflective surface of the reflector. In addition, the manufacture of the reflector makes relatively easy.
The horizontal reflective surface close to the light source is positioned so as to reflect light back to a wide range of an illumination surface of the backlight illuminator. The intermediate angled reflective surface or the intermediate concavely curved reflective surface and the angled reflective surface distant from the light source are positioned so as to reflect light back to the corresponding illumination surfaces in such a manner that the reflected light overlaps the light reflected from the horizontal reflective surface. Thus, the reflective surface close to the light source, the intermediate reflective surface and the reflective surface distant from the light source are positioned relative to one another so as to intensively reflect light back to an intermediate region of neighboring two linear light sources so that excellent brightness and uniformity of brightness can be ensured on the entire illumination surface of the backlight illuminator.
The present invention has been made on the basis of the foregoing findings.
According to an aspect of the present invention, a backlight illuminator comprises a plurality of linear light sources arranged in parallel, and a reflector arranged symmetrically about each linear light source along each light source so as to reflect light from each linear light source back to a surface to be illuminated. The reflector includes a reflective region formed in symmetry on both sides of each of the light sources. The reflective region includes three reflective surfaces, namely a reflective surface close to the light source, an intermediate reflective surface, and a reflective surface distant from the light source. The reflective surface close to the light source is formed to have a horizontal surface so as to reflect light back to a region A of the surface to be illuminated. The intermediate reflective surface is formed into either an angled surface slanted with respect to the horizontal surface or a curved surface concavely curved with respect thereto so as to reflect light back to a region B of the surface to be illuminated. The reflective surface distant from the light source is formed into an angled surface slanted with respect to the horizontal reflective surface so as to reflect light back to a region C of the surface to be illuminated. The illumination ranges of the regions B and C of the surface to be illuminated are overlapped with the illumination range of the region A of the surface to be illuminated, respectively. The illumination range of the region B extends over the intermediate position of neighboring two light sources and overlaps the illumination surface on the side of the neighboring light source by approximately 0% to 20% of a distance between the light source and the intermediate position. Similarly, the illumination range of the region C extends over the intermediate position of the neighboring two light sources and overlaps the illumination surface on the side of the neighboring light source by approximately 0% to 10% of the distance between the light source and the intermediate position.
The illumination range of the region B has a narrower width than the illumination range of the region C, and the illumination range of the region B is located closer to the intermediate position of the neighboring two light sources than the illumination range of the region C.
An angle of inclination of the reflective surface distant from the light source is a right angle or an acute angle of about 70 degrees or more with respect to an adjacent reflective surface distant from the light source.
In an embodiment of the present invention, the intermediate reflective surface connected to the reflective surface distant from the light source and the reflective surface close to the light source is formed into a single reflective surface having an upward angled surface or a concavely curved surface.
This and other objects, features, and advantages of the present invention will become more apparent from reading of the following detailed description in connection with the accompanying drawings.